Alumina phosphated with partial ester

ABSTRACT

An alumina-containing material is phosphated with mono- and dialkylphosphate esters. These partial phosphate esters are produced by a solvolysis reaction of a phosphorus compound and an alcohol. The phosphated alumina-containing material, when combined with a transition metal, such as chromium, can be used as a polymerization catalyst system to polymerize mono-1-olefins.

This application is a division of application Ser. No. 07/075,457, filedJuly 20, 1987, now U.S. Pat. No. 4,960,748.

BACKGROUND OF THE INVENTION

This invention relates to phosphated supports for chromium containingolefin polymerization catalysts. This invention also relates to aprocess to polymerize olefins.

Supported chromium oxide catalyst systems can be used to prepare olefinpolymers in a hydrocarbon solution to give a product having excellentcharacteristics from many standpoints. Supported chromium oxide catalystsystems can also be used to prepare olefin polymers in a slurry systemwherein the polymer is produced in the form of small particles of solidmaterial suspended in a diluent. This process, frequently referred to asa particle-form process, has the advantage of being less complex.However, certain control operations which are easily carried out in thesolution process are considerably more difficult in the particle-formprocess. For instance, in the solution process, control of the polymermolecular weight can be effected by changing the temperature, with lowermolecular weight (higher melt flow) being obtained at the highertemperature. However, in the slurry process, this technique isinherently limited since any efforts to increase the melt flow to anyappreciable extent by increasing temperature would cause the polymer togo into solution and thus destroy the slurry or particle form process.Also, it is frequently desired to have a polymer with a broadermolecular weight distribution than is normally obtained in the slurry orparticle-form process in order to facilitate blow molding of the olefinpolymer.

It is known in the art that the activity of such chromium oxide catalystsystems can be improved by treating the support withphosphorus-containing compounds. However, the resultant catalyst systemusually tends to contain less phosphorus than a theoretical calculationwould indicate should have been added. Additionally, it is desired toincrease the surface area of such a catalyst system so as to improvepotential productivity. Known phosphorus-containing catalyst system areirregularly shaped, i.e. not spherical, making them more difficult totransport and yielding an inferior polymer. It is also desired to have acatalyst system which is easy to manufacture.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a catalyst system capableof giving both a high melt flow and a broad molecular weightdistribution olefin polymer.

It is a further object of this invention to provide a catalyst systemwhich produces a high molecular weight olefin polymer and which isespecially sensitive to molecular weight control agents, such ashydrogen and/or a cocatalyst, so that a single catalyst can produce acomplete spectrum of polymers so far as melt flow is concerned.

It is a further object of this invention to provide a catalyst systemsuitable for use in slurry polymerization systems.

It is a further object of this invention to provide a catalyst systemcapable of giving a polymer suitable for blow molding, film and otherapplications requiring a moderate to relatively high melt flow and atleast a fairly broad molecular weight distribution. It is an object ofthis invention to provide a catalyst system which retains nearly all ofthe phosphorus actually added.

It is a further object of this invention to provide a catalyst systemwherein the phosphorus-containing support has an increased surface area.

It is a further object of this invention to produce a spherically shapedcatalyst system.

It is yet a further object of this invention to produce a catalystsystem wherein the phosphating agent and chromium compound can be addedsimultaneously.

It is yet another object of this invention to provide an improvedprocess for the polymerization of olefins.

In accordance with this invention, an alumina-containing support for achromium-containing olefin polymerization catalyst system is phosphatedwith a partial phosphate ester.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Support

The support of the catalyst of this invention is a phosphatedalumina-containing material.

The starting alumina-containing material can contain any aluminaconvertible at least in part on thermal dehydroxylation to gammaalumina. Preferably, it is boehmite alumina. It may be desirable in someinstances to prepare the alumina-containing support in the presence ofabout 1 to about 30 mole percent of a boron compound, such as boricacid, based on the moles of alumina. Other metal oxides, such as boria,magnesia, thoria, titania, zirconia, or mixtures thereof, can be presentwithout adverse effects. Other ingredients which do not adversely affectthe catalyst, or which are present to produce some unrelated result, canalso be present, so long as the support is at least 50 weight percentalumina. The alumina-containing material can also contain otheringredients which do not adversely affect the quality of the finalcatalyst, such as silica, but can be essentially pure alumina.

In the case where a silica-alumina containing material is used for thesupport, the material generally comprises a range of about 0.01 to about50 weight percent silica. Preferably, the silica will comprise about0.05 to about 25 weight percent and a range of about 0.1 to about 10weight percent silica is most preferred for best control of theresultant polymer. The pore volume of the silica-alumina is the range ofabout 0.5 to about 2.5 milliliters per gram (ml/g), preferably in therange of about 1 to about 1 ml/g for greater durability. The surfacearea of the silica-alumina is in the range of about 100 to about 500square meters per gram (M² /g), preferably in the range of about 200 toabout 400 m² /g, and most preferably in the range of about 250 to about350 m² /g, for easier phosphate and catalyst loading, improved activity,and greater durability.

Prior to treatment with a phosphating agent, it is preferred that thealumina-containing support be calcined at a temperature in the range ofabout 450° to about 900° C., preferably at about 600° to about 800° C.,for a time of about one minute to about 48 hours, preferably about 0.5to about 10 hours. The calcining can be carried out in an oxidizing,inert, or reducing atmosphere; the principal purpose of the atmosphereis to sweep away moisture.

The term "phosphated" is meant to describe the alumina-containingsupport treated with a phosphorus compound as described herein and notnecessarily to means that phosphate groups are attached to thealumina-containing support. Probably any reaction with thealumina-containing support takes place on activation. The terms"phosphate treatment" and "phosphating" are meant to refer broadly tothe phosphorus treatment and not to indicate that the treating agent isa phosphate; although, of course, on activation the phosphorus will beconverted to a phosphate.

The phosphating agent used to prepare a partial phosphate ester, isdissolved in alcohol and can be any source of phosphate ions.Preferably, anhydrous phosphorus pentoxide, P₂ O₅, also designated as P₄O₁₀, is the source of phosphate ions; although P₂ O₄ and P₂ O₃, alsodesignated as P₄ O₆, can be used as the source of phosphate ions. Thealcohol can be any ROH compound, wherein R is any alkyl groups whichcomprises from one to four carbon atoms. Preferred alcohols include, butare not limited to, methanol, ethanol, propanol, isopropanol, 1-butanol,2-butanol, iso-butanol, and mixtures thereof. The solvolysis reaction ofanhydrous phosphorous pentoxide in alcohol yields primarily a mixture ofmono- and dialkyl phosphate esters, as the following reaction schemeillustrates:

    ROH+P.sub.2 O.sub.5 OP(OH).sub.2 OR+OP(OR).sub.2 OH

Preferably, the alumina-containing support is phosphated by a modifiedincipient wetness technique. It is believed that this techniquephosphates only the surface of the alumina-containing support. Themodified incipient wetness technique requires a minimum amount ofsolvent used with the phosphate ions during the phosphating treatment.Initially, the desired phosphorus to aluminum mole ratio must bedetermined. Then, the moles of phosphorus to be added as the solute iscalculated; finally, the grams of phosphating agent to be used iscalculated. The volume of alcohol to be used as the solvent isdetermined based on the pore volume of the alumina-containing support tobe phosphated. The known pore volume of the alumina-containing supportis multiplied by the grams of alumina-containing support to bephosphated, to give the minimum volume of alcohol in which to dissolvethe phosphating agent.

The volume of alcohol used can be increased slightly, so that upon theaddition of the phosphorus-alcohol solution to the alumina-containingsupport, the support looks wet, but not a slurry. The incipient wetnesstechnique, hence, does not overly saturate the alumina-containingsupport. After treatment, the unreacted alcohol is removed by drying,for instance, by gentle heating in a vacuum, or by means of gentleheating in the presence of an anhydrous gaseous stream, such as nitrogenor air.

The phosphorus component is added in an amount in the range of about 0.1to about 20, preferably about 1 to about 10, mole percent of thephosphorus compound incorporated, based on the total moles ofalumina-containing support. Based on surface area, the phosphoruscompound from the phosphating agent is present in an amount sufficientto give about 0.005 to about 1, preferably about 0.01 to about 0.5milligrams of phosphorus per square meter (mg P/m²) of thealumina-containing material surface as measured by BET nitrogenadsorption.

In compositions containing chromium, the phosphorus component, based onthe chromium content, is utilized in an amount to give about 1 to about5 atoms percent of phosphorus incorporated. This is about 1 to about 5atoms of phosphorus per atoms of chromium, particuarly when thepreferred 1 weight percent chromium, based on the weight ofalumina-containing support, is used. Generally, the ratio of atoms ofphosphorus per atom of transition metal, such as chromium, will be inthe range of about 0.1 to about 20, preferably about 1 to about 10.

Viewed another way, the phosphating agent is used in a sufficient amountto give a phosphorus to total aluminum atom ratio of about 0.02 to about1:1, preferably about 0.05:1 to about 0.6:1 for most efficient use ofthe phosphating agent.

Since the phosphating treatment of this invention phosphates only thesurface of the aluminum-containing material, the phosphorus to aluminumatom ratio can also be expressed in terms of a phosphorus to surfacealuminum atoms ratio. The phosphorus to surface aluminum atom ratio isabout 0.2:1 to about 2:1, preferably about 0.6:1 to about 0.9:1 for mostefficient use of the phosphating agent.

In practice, however, it is possible to use as much phosphating agent asdesired with the excess simply being washed off after the phosphatingtreatment is complete. The phosphating treatment is generally carriedout at a temperature in the range of about 15° to about 500° C.,preferably in the range of about room temperature to about the boilingpoint of the solvent of the phosphate solution used. The contact timebetween the phosphorus-alcohol solution and the alumina-containingsupport is in the range of about 1 minute to about 2 hours, preferablyin the range of about 2 minutes to about 30 minutes. These temperatureand time parameters produce the appropriately phosphatedalumina-containing support.

The calcined and phosphated alumina-containing support of this inventionhas wide applicability in utilities where refractory catalyst supportsare used. The calcined and phosphated alumina-containing support of thisinvention can also be used in other utilities known for alumina, such asfillers. It has also been found to be an excellent isomerizationcatalyst without any other catalytic ingredient being deposited thereon.However, it is of primary utility as a chromium oxide catalyst supportfor olefin polymerization.

It has been found from work with aluminum phosphate, that the bestpolymer properties, such as high melt index, high density and goodenvironmental stress crack resistance (ESCR) are obtained using a highphosphorus to total aluminum ratio, i.e., about 0.8. However, surfacearea and pore volume are optimum at a lower phosphorus to total aluminumratio, i.e. about 0.4 because of sintering at the higher ratios. Thisinvention makes it possible to have the good physical stability of a lowP/Al ratio support since the bulk of the support is alumina and stillhave the good catalytic effect of the high ratio because of the highcontent of phosphorus on the surface. In addition, the invention allowsachieving a high productivity with a relatively inexpensivealumina-containing support, such as silica-alumina.

The invention takes advantage of the fact that some properties, such assurface area, are favored by high alumina content whereas others, suchas melt index potential, are favored by phosphate content. By impartinga phosphate layer on the surface of the silica-alumina, it is possibleto take advantage of both trends, and by calcining prior to thephosphating, it is possible for reasons which are not fully understood,to drastically improve the activity and let index potential of thecatalyst system.

Catalyst

Catalyst systems employed in the practice of this invention comprise aphosphated predominately alumina support, prepared as described above,and a transition metal compound, such as chromium. Other suitable, butless preferred, transition metal compounds are vanadium and titaniumcompounds. It should be recognized, however, that catalyst systems ofthe invention can be used in conjunction with additional polymerizationcomponents which do not adversely affect the catalyst performance, suchas a cocatalyst.

The transition metal compound can be introduced anytime prior toactivation of the catalyst system. Where the transition metal compoundis chromium, the chromium compound can be any chromium compound in, orconvertible to, the hexavalent state which is soluble in any non-aqueoussolvent. The catalyst system contains chromium in an amount generallywithin the range of 0.001 to about 10, preferably about 0.1 to about 5,more preferably about 1 weight percent, based on the weight of thedried, phosphated alumina-containing support.

Catalyst concentrations can be such that the supported catalyst contentranges from 0.001 to about 1 weight percent based on the weight of thereactor contents.

The chromium compound can be incorporated as known in the art. Forinstance, a hydrocarbon solution of a material such as tertiarybutylchromate can be used to impregnate the phosphatedalumina-containing support or chromium can be added along withphosphorus-alcohol solution to the alumina-containing support. Thenon-aqueous, hydrocarbon solvent for the chromium compound can be anycommon solvent, such as toluene, benzene, heptane, hexane, etc. For easeof catalyst system preparation, the chromium compound is dissolved in analcohol having one to four carbon atoms, such as methanol, ethanol,propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, and mixturesthereof.

Alternatively, the support can be activated without a transition metalcomponent being present, and thereafter, a chromium component such as anorganochromium compound, chromocene, for instance, can be anhydrouslyimpregnated onto the support and the solvent gently removed to give anactive catalyst.

The chromium-alcohol and phosphorus-alcohol solutions can be combinedand added to the alumina-containing support simultaneously. However, ingeneral, it is preferred to prepare the phosphated alumina-containingsupport prior to adding the chromium component. Most preferably, thephosphated alumina-containing support is heated prior to addition of thechromium. Calcination of the phosphated, alumina-containing material isin an oxygen-containing atmosphere, at a temperature in the range ofabout 500° C. to about 1000° C. for a time in the range of about 1minute to about 48 hours, prior to contacting a transition metalcompound, such as chromium. Thus, in this preferred embodiment, thesupport is heated twice, once after the phosphorus is added and thenagain after the chromium compound is added. In all aspects of thiscatalyst embodiment of the invention, the catalyst system of thephosphated silica-alumina support and the chromium compound must beactivated, i.e., heated, to activate the catalyst for polymerization.

The activation of the chromium-containing systems can be carried out ata lower temperature than is generally required for activatingpredominately silica based chromium catalyst systems. Temperatures inthe range of about 150° to about 900° C., preferably about 300° to about800° C., more preferably about 500° to about 750° C. are suitable. Theactivating ambient can be any oxidizing ambient but for reasons ofconvenience is generally air. Times of about one minute to about 48hours are preferred, with times of about 0.5 to about 10 hours morepreferred. This activation can be carried out at atmospheric pressures,but a vacuum is preferred to maintain the structural integrity of thecatalyst system. Vacuum drying helps prevent combustion of the solventto form water which has pernicious effects on the catalyst.

The catalyst systems of this invention, comprising chromium on aphosphated alumina-containing support, can be subjected to reduction andthen reoxidation as disclosed in McDaniel, U.S. Pat. No. 4,182,815 (Jan.8, 1980), disclosure of which is hereby incorporated by reference, ifdesired.

Cocatalysts

The catalysts of this invention can be used in conjunction with acocatalyst if desired. Suitable cocatalysts include aluminum and boronalkyls, which if used, increase the melt flow characteristics of theresultant polymer. The most preferred boron compounds are trihydrocarbylboron compound, particularly tri-n-butylborane, tripropylborane, andtriethylborane (TEB). Other suitable boron compounds include trialkylboron compounds broadly, particularly those having alkyl groups of about1 to about 12 carbon atoms, preferably, about 2 to about 5 carbon atoms;triaryl boron compounds such as triphenylborane; boron alkoxides such asB(C₂ H₅)₂ OC₂ H₅ ; and halogenatedalkyl boron compounds such as BC₂ H₅Cl₂. Suitable aluminum alkyls include R'₃ Al, and R'AlX₂ compounds whereR' is a hydrocarbyl radical with about 1 to about 12 carbon atoms and Xis a halogen, preferably chlorine. Triethylaluminum and diethylaluminumchloride are particularly suitable.

The cocatalyst is used in an amount within the range of about 0.1 toabout 25, preferably about 0.25 to about 10, parts per million based onthe solvent or diluent in systems employing a solvent or diluent andbased on total reactor contents in systems not employing a solvent ordiluent. Based on the chromium in the catalyst, they are used in anamount so as to give about 0.05 to about 5, preferably about 0.05 toabout 3 times as much boron by weight as chromium by weight. Based onatoms of boron per atoms of chromium, the amount of cocatalyst used willgive about 0.5 to about 14, preferably about 1.5 to about 10, atoms ofboron (or aluminum) per atom of chromium. The boron cocatalysts givehigher density olefin polymers than aluminum cocatalyst or catalystsystems with no cocatalyst.

The cocatalyst can be either premixed with the catalyst system orintroduced into the reactor as a separate stream, the latter being thepreferred procedure for ease of catalyst system preparation andhandling.

Of course, the final catalyst can be used with, or contain, otheringredients which do not adversely affect its performance, as forexample other cocatalyst, antistatic aids in the polymerization zone,and other conventional ingredients.

Reactants

Reactants applicable for use with the catalysts and processes of thisinvention are olefinic compounds which can polymerize, i.e., react, withother olefinic compounds. The catalysts of the invention can be used topolymerize at least one mono-1-olefin having 2 to about 8 carbon atomsper molecule. Exemplary compounds include, but are not limited to,ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene.

This invention is of particular applicability in producing ethylenehomopolymers and copolymers from mixtures of ethylene and about 0.5 toabout 20 mole percent of one or more comonomers selected from 1-olefinshaving about 3 to about 8 carbon atoms per molecule. Exemplarycomonomers include, but are not limited to, aliphatic 1-olefins, such aspropylene, 1-butene, 1-pentene, 1-hexene, 1-octene and other higherolefins and conjugated or non-conjugated diolefins such as1,3-butadiene, isoprene, piperylene, 2,3-dimethyl-1,3-butadiene,1,4-pentadiene, 1,7-hexadiene, and other such diolefins and mixturesthereof. Ethylene copolymers preferably constitute at least about 90,preferably about 97 to about 99.6 weight percent polymerized ethyleneunits. Propylene, 1-butene, 1-pentene, 1-hexene and 1-octene areespecially preferred comonomers for use with ethylene.

The presence of comonomer has a tendency to increase melt flow more thanwould be expected. Hence, the use of only a small amount of comonomer,say 0.001 to 0.3, preferably 0.01 to 0.1, mole percent in the feed canbe used to give a polymer which is essentially a homopolymer but whichhas increased melt flow.

Reaction Conditions

The polymers can be prepared from the catalyst system of this inventionby solution polymerization, slurry polymerization, and gas phasepolymerization techniques using conventional equipment and contactingprocesses. Contacting of the monomer or monomers with the catalystsystem can be effected by any manner known in the art of solidcatalysts. One convenient method is to suspend the catalyst system inthe organic medium and to agitate the mixture to maintain the catalystsystem in suspension throughout the polymerization process. Other knowncontacting methods such as fluidized bed, gravitating bed, and fixed bedcan also be employed. Catalyst systems form process as disclosed inWitt, U.S. Pat. No. 3,724,063 the disclosure of which is herebyincorporated by reference.

The catalyst systems of this invention are particularly suitable for usein slurry polymerizations. The slurry process is generally carried outin an inert diluent (medium), such as a paraffin, cycloparaffin oraromatic hydrocarbon. For predominantly ethylene polymers, a temperaturerange of about 66° to about 110° C. is employed.

The medium and temperature are selected such that the polymer isproduced as solid particles and is recovered in that form. Pressures inthe particle form process can vary from about 110 to about 700 psia(0.76-4.8 MPa) or higher. The catalyst system is kept in suspension andis contacted with the amount or monomers at sufficient pressure tomaintain the medium and at least a portion of the monomer or monomers inthe liquid phase.

Generally in slurry polymerization of ethylene homopolymer andpredominantly ethylene copolymer systems, the feasible temperature rangeis about 93° to about 110° C. Commercial systems are operated as closeto the maximum as possible, i.e., about 107°±3° C., in order to obtainthe highest possible melt index without the polymer going into solution.Catalyst systems of this invention allow operating at the low end tothis range, i.e., about 96°±3° C., in systems normally employing atemperature of about 107° C. The lower temperature gives a relativelyhigher monomer partial pressure, thus giving higher activity.

Hydrogen can be added to the reactor to control the molecular weight ofthe polymer. Generally, hydrogen concentration is inversely proportionalto the molecular weight of the polymer, i.e., increasing hydrogenpressure decreases the polymer molecular weight. In prior art, hydrogenis generally used at pressures up to about 120 psia (0.8 MPa),preferably within the range of about 20 to about 70 psia (about 0.01 toabout 0.48 MPa). Similar amounts can be used in accordance with thisinvention although smaller amounts are sometimes preferred because ofthe sensitivity of this catalyst system to the effects of hydrogen.

EXAMPLES EXAMPLE I

In this example, silica-alumina supports were spray-driedsilica-aluminas having a boehmite structure. These silica-aluminas aresold by Ketjen Catalysts, a division of Akzo Chemie, under the trademarkKetjen L, which has about 5 weight percent silica. The invention runswere calcined at 600°-700° C. in air before being given a phosphatingtreatment. This calcination dehydroxylates the alumina converting itfrom boehmite structure to the gamma structure. The phosphatingtreatment was carried out by impregnating the silica-alumina with analcoholic solution of the phosphorus compound listed. An amount ofalcoholic solution was used which was just sufficient to impartincipient wetness to the support, this generally being about 2.5milliliters of alcoholic solution per gram of support (cc/g).

The phosphorus to total aluminum ratio of the catalyst was adjusted byvarying the amount of phosphorus compound used. Generally, 0.5 to 3grams/40 cc of alcohol was used. The phosphated silica-alumina wascalcined in air at about 700° C. and then analyzed for phosphoruscontent.

The data in Table I shows the variation between the theoreticallycalculated and the actually analyzed amount of phosphorus anhydrouslyloaded onto a pre-calcined silica-alumina.

                  TABLE I    ______________________________________            Phosphorus (Total) P/A1 Mole Ratio    Run No.   Compound     Calculated                                     Analyzed    ______________________________________    101       OP(OC.sub.2 H.sub.5).sub.3                           0.20      0.08    102       OP(OC.sub.2 H.sub.5).sub.3                           0.28      0.10    103       OP(OC.sub.4 H.sub.5)                           0.20      0.15    104       OP(OC.sub.4 H.sub.5)                           0.25      0.20    105       P.sub.2 O.sub.5 /i-PrOH                           0.10      0.12    106       P.sub.2 O.sub.5 /i-PrOH                           0.30      0.32    107       H.sub.3 PO.sub.4                           0.16      0.17    ______________________________________

Runs 101 through 104 were trialkylphosphate esters. The decrease in theP/Al (total) ratio, from the calculated ratio to the analyzed ratio,indicates that some of the phosphorus compound volatilizes off thesurface of the alumina during calcination. Runs 105 and 106, wherein P₂O₅ and isopropyl alcohol from mono- and dialkylphosphate esters (i.e.,partial esters), show relatively good agreement in both P/Al (total)ratios. When phosphoric acid is used as the phosphating agent, run 107,there is also good agreement between the P/Al ratios.

EXAMPLE II

Each run in Example II was conducted in a clean, dry, air-free, stirred,stainless steel reactor of about 2-liter capacity. About 600 grams ofisobutane was used in each run as diluent with a catalyst charge rangingfrom about 0.05 to about 0.1 grams. The reactor and its contents wereheated to the desired operating temperature, about 95° C., and ethylenewas pressured in to give about 565 psia (3.9 MPa). Triethylborane (TEB)was added to the reactor to give a concentration of about 8 parts permillion TEB. The run was started immediately because the catalysts,unlike the corresponding chromium oxide on silica catalysts, do not havean induction period. Ethylene pressure was maintained during the run bysupplying additional ethylene as required from a reservoir.

Each run was terminated by stopping the ethylene flow and venting thegaseous reactor contents to a flare line for disposal. The productivitywhich is expressed in terms of grams polyethylene per gram catalyst.

The data in Table II demonstrate the effect phosphorus loading has onsurface area, productivity, and the resultant polymer high load meltindex (HLMI). The silica-alumina, Ketjen L, was calcined both before andafter treatment with the phosphorus and chromium compounds. Thephosphating treatment of the invention (runs 201-210) was carried out byimpregnating the silica alumina with an alcoholic solution of phosphoruspentoxide and chromium acetate. The support of the control runs wasphosphated with an alcoholic solution of phosphoric acid and chromiumacetate. A sufficient amount of the alcoholic solution was used toimpart incipient wetness to the support. Thus, about 2.5 milliliters ofalcoholic solution was added for each gram of support.

                  TABLE II    ______________________________________                    P/A1    Run  Phosphating                    Mole    Surface    No.  Agent      Ratio   Area, m.sup.2 g                                    Activity.sup.(1)                                            HLMI.sup.(2)    ______________________________________    201  P.sub.2 O.sub.5                    0.1218  278     --      0    202  P.sub.2 O.sub.5                    0.1222  279     2944    2.98    203  P.sub.2 O.sub.5                    0.1599  275     5727    --    204  P.sub.2 O.sub.5                    0.1761  290     4038    6.93    205  P.sub.2 O.sub.5                    0.2100  267     2783    9.5    206  P.sub.2 O.sub.5                    0.2193  283     2903    12.5    207  P.sub.2 O.sub.5                    0.2425  282     3563    --    208  P.sub.2 O.sub.5                    0.2656  243     2322    30.5    209  P.sub.2 O.sub.5                    0.3214  268     2491    61.3    210  P.sub.2 O.sub.5                    0.39    242     1544    44    211  H.sub.3 PO.sub.4                    0.1     275     1276    --    212  H.sub.3 PO.sub.4                    0.1092  303     2756    --    213  H.sub.3 PO.sub.4                    0.1134  270     3252    6.7    214  H.sub.3 PO.sub.4                    0.15    --      3160    19.8    215  H.sub.3 PO.sub.4                    0.1710  256     2641    45.6    216  H.sub.3 PO.sub.4                    0.1741  237     2257    9.4    217  H.sub.3 PO.sub.4                    0.2     202     1178    --    218  H.sub.3 PO.sub.4                    0.2122  222     1740    7.7    219  H.sub.3 PO.sub.4                    0.2166  211     3225    82.8    220  H.sub.3 PO.sub.4                    0.2402  198     3319    83.3    ______________________________________     .sup.(1) grams of polymer produced per gram of catalyst in 30 minutes     (g/g/30).     .sup.(2) ASTM D1238, Condition F.

Comparison of the P₂ O₅ data to the H₃ PO₄ data shows that, in general,the surface area of the silica-alumina phosphated with P₂ O₅ -alcohol(partial esters) is greater than the H₃ PO₄ phosphated silica-alumina.The corresponding activity of the P₂ O₅ phosphated silica-aluminacatalyst is also generally greater than the H₃ PO₄ phosphatedsilica-alumina. The HLMI data reveals that P₂ O₅ phosphatedsilica-alumina has lower high load melt indices than the H₃ PO₄phosphated silica-alumina. Thus, the P₂ O₅ /ROH treatment allows morephosphorus to be added to the silica-alumina with less effect on theHLMI and surface area and a greater effect on activity than the H₃ PO₄/ROH system.

While this invention has been described in detail for the purpose ofillustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

That which is claimed is:
 1. A polymerization process comprisingcontacting at least 1 mono-1-olefin having 2 to 8 carbon atoms permolecule with a catalyst system produced by;(a) heating analumina-containing material at a temperature in the range of about 450°to about 900° C., for a time in the range of about 1 minute to about 48hours; (b) treating the thus heated material with an alcohol solution ofpartial phosphate ester to give a phosphated alumina-containingmaterial, wherein said partial phosphate ester comprises a mixture ofmono- and dialkyl phosphate esters produced by combining phosphorusesters produced by combining phosphorus pentoxide with an alcohol; and(c) combining the phosphated alumina-containing material with a chromiumcompound.
 2. A process according to claim 1 wherein said olefin isselected from the group consisting of ethylene, propylene, 1-butene,1-pentene, 1-hexene, and 1-octene.
 3. A process according to claim 2wherein said olefin is predominantly ethylene.
 4. A process according toclaim 3 wherein a comonomer having from about 3 to about 8 carbon atomsper molecule is copolymerized with ethylene to form an ethylenecopolymer.
 5. A process according to claim 4 wherein said comonomer isselected from the group consisting of propylene, 1-butene, 1-hexene, and1-octene.
 6. A process according to claim 4 wherein said ethylenecopolymer constitutes at least about 90 weight percent polymerizedethylene units.
 7. A process according to claim 1 wherein saidpolymerization is carried out at a temperature with the range of about93° to about 110° C.
 8. A process according to claim 1 wherein saidalumina-containing material contains about 0.01 to about 50 weightpercent silica.
 9. A process according to claim 8 wherein saidalumina-containing material has a surface area in the range of about 100to about 500 m² /g.
 10. A process according to claim 8 wherein saidalumina-containing material has a pore volume in the range of about 0.5ml/g to about 2.5 ml/g.
 11. A process according to claim 1 wherein saidalcohol is selected from the group consisting of methanol, isopropanol,1-butanol, 2-isobutanol and mixtures of two or more thereof.
 12. Aprocess according to claim 1 wherein said treatment with said partialphosphate ester is sufficient to give a range of about 0.1 to about 20mole percent of phosphorus based on the total moles of saidalumina-containing material.
 13. A process according to claim 1 whereinsaid treatment with said partial phosphate ester is sufficient to give arange of about 0.01 to about 0.5 milligrams phosphorus per square meterof surface area of said alumina-containing material.
 14. A processaccording to claim 1 wherein said chromium compound is selected from thegroup consisting of chromium trioxide, chromium acetate, chromiumnitrate and mixtures of two or more thereof; andwherein said chromiumcompound is present in the range of about 0.1 to about 5 weight percent,based on the weight of said phosphated alumina-containing material. 15.A process according to claim 1 wherein said chromium compound iscombined with alcohol prior to contacting said phosphatedalumina-containing material.
 16. A process according to claim 1 furthercomprising calcining said phosphated alumina-containing material in anoxygen-containing atmosphere, at a temperature in the range of about500° to about 1000° C., for a time in the range of about 1 minute toabout 48 hours, prior to contacting said chromium metal compound.
 17. Aprocess according to claim 1 further comprising dissolving said partialphosphate ester and said chromium compound separately in alcohol,combining the two solutions, and then adding said combined solution tosaid alumina-containing material.
 18. A process according to claim 1wherein said catalyst system comprising said chromium compound on saidphosphated alumina-containing material is heated in an elevatedtemperature in an oxygen-containing atmosphere.
 19. A process accordingto claim 1 further comprising combining said catalyst system with anorgano-metal cocatalyst.
 20. A polymerization process comprisingcontacting at least one mono-1-olefin having 2 to 8 carbon atoms permolecule with a catalyst system produced by;(a) calciningsilica-alumina, comprising from about 0.1 to about 50 weight percentsilica, at a temperature in the range of about 450° to about 900° C.,for a time in the range of about 1 minute to about 48 hours; (b)dissolving phosphorus pentoxide in alcohol; (c) dissolving a chromiumcompound in alcohol; (d) combining the solutions of (b) and (c); (e)treating the calcined silica-alumina of (a) with a solution of (d); and(f) calcining the compound of (e) in an oxidizing ambient at atemperature in the range of about 150° to about 900° for a time in therange of about 1 minute to about 48 hours.
 21. A process according toclaim 20 wherein said olefin is selected from the group consisting ofethylene, propylene, 1-pentene, 1-hexene, and 1-octene.
 22. A processaccording to claim 20 wherein said olefin is predominantly ethylene. 23.A process according to claim 22 wherein a comonomer having from about 3to about 8 carbon atoms per molecule is copolymerized with ethylene toform an ethylene copolymer.
 24. A process according to claim 23 whereinsaid comonomer is selected from the group consisting of propylene,1-butene, 1-hexene, and 1-octene.
 25. A process according to claim 23wherein said ethylene copolymer constitutes at least about 90 weightpercent polymerized ethylene units.
 26. A process according to claim 1wherein a polymer is recovered.
 27. A process according to claim 20wherein a polymer is recovered.